Figure 2

Model of GtrIV with all residues shown. Residues in pink are the 15 negatively charged amino acids present in loop No. 6. There are three negatively charged amino acid pairs DE261, ED283 and ED326. Deletion experiments for loop No. 2 involved deleting all the residues highlighted in brown, while a deletion in loop No. 3 was brought about by deleting all the residues highlighted in red. In loop No. 6, 4 different loop deletions were created. To investigate the importance of the negatively charged residues, all residues between the two black lines, which include all 15 negatively charged amino acids were deleted. To further investigate which sets of negatively charged residues were important, amino acids highlighted in green (loop No. 6 partial deletion 3), blue (loop No. 6 partial deletion 2) and orange (loop No. 6 partial deletion 1) were deleted separately.